Vascular disease accounts for increased morbidity and mortality in diabetes. Risks of macrovascular complications are significantly enhanced in diabetic patients. However, the molecular basis for diabetic atherosclerosis is incompletely understood. Diabetic patients have increased propensity for vascular smooth muscle cell (VSMC) migration and proliferation, hallmark of VSMC phenotypic switching, contributing to atherosclerosis. Activation of hexosamine metabolic pathway leads to enhanced O-linked N- acetylglucosamine (O-GlcNAc) modification of intracellular proteins. However, a mechanistic link between O- GlcNAc signaling and VSMC activation to an athero-prone phenotype in diabetes remains unknown. Relevant to this application are findings that atherosclerotic lesion formation correlates with expression of O-GlcNAc transferase (OGT), regulator of O-GlcNAc signaling, in aortic vessels of diabetic atherosclerotic mice. The overall hypothesis is that OGT induces VSMC de-differentiation to an ?athero-prone? phenotype via activation of specific molecular pathways in diabetes. We further postulate that targeted OGT deletion in aortic SMC will blunt these pathways blocking development of atherosclerotic complications in diabetes. The specific aims are: 1) We will determine the molecular mechanisms by which OGT induces VSMC transition to an atherogenic phenotype in diabetes, 2) We will interrogate whether OGT plays a direct role in development of atherosclerotic complications in diabetes. This will be tested via loss of function and rescue approaches in vitro using primary cultures of human aortic SMC under diabetic milieu and atherosclerotic mouse models of Type 1 and Type 2 diabetes, with aortic SMC-specific OGT deletion in vivo. We will utilize different biochemical, histological and molecular biology studies in combination with ultrasound imaging, en-face atherosclerotic lesion assay, proteomics and bone-marrow transplantation strategies. Overall, this proposal will uncover a novel role of OGT in the etiology of diabetic vascular disease. Such information will advance our fundamental understanding of the molecular basis of diabetic vasculopathy and open avenues for novel discoveries such as cell-specific OGT-targeted therapies for diabetic macrovascular complications.